Intercalation Compounds Research Articles

Potassium storage behavior and low-temperature performance of typical carbon anodes in potassium-ion hybrid capacitors enabled by Co-intercalation graphite chemistry

Carbon materials are widely explored as anodes for potassium-ion storage, yet the slow K+ desolvation process in electrolyte at low temperatures presents a kinetic limitation that impedes reliable operation in specific conditions. In this work, we systematically investigate the potassium storage behavior of four typical carbon materials—graphite, hard carbon, activated carbon, and graphene—in a 1 M KFSI-Diglyme electrolyte, highlighting a co-intercalation approach that significantly reduces the desolvation energy barrier. The formation of ternary graphite intercalation compounds (t-GICs) through co-intercalation in graphite introduces weak interlayer interactions between the graphite layers and solvated K+, which accelerate K+ diffusion in the anode, thereby enhancing reaction kinetics. This unique mechanism enables the graphite anode to deliver remarkable rate performance (98 mAh g−1 at 0.05 A g−1 and 76 mAh g−1 at 1 A g−1) even at −20 °C. Furthermore, potassium-ion hybrid capacitors (PICs) using the graphite anode achieve impressive cycling stability, with 88 % capacity retention after 2000 cycles at 2 A g−1 and a high power density of 11.1 kW kg−1 (57 Wh kg−1) at −20 °C. These findings provide key insights into the design of robust potassium-ion storage devices capable of sustaining high performance in low-temperature environments.

DABCO-Intercalated α-Zirconium Phosphate as a Latent Thermal Catalyst in the Reaction of Urethane Synthesis

The mixture of hexamethylene diisocyanate (HDI) and butanol (BuOH) with the intercalation compound of 1,4-diazabicyclo[2.2.2]octane (DABCO) with α-zirconium phosphate (α-ZrP) has been evaluated as a latent thermal catalyst at varying temperatures. α-ZrP·DABCO did not show activity at 25 °C, but showed a high level of activity at a higher temperature of 80 °C. To clarify the reaction behavior of HDI-BuOH with α-ZrP·DABCO, a viscosity value of 1200 mPa·s·g/cm2 was reached at 80 °C for 30 min. To investigate the deintercalation behavior of DABCO from the α-ZrP interlayer, it was investigated in BuOH and in HDI, respectively, under heated conditions. Interestingly, XRD patterns showed a reduction in α-ZrP·DABCO for the interlayer distance due to the deintercalation of DABCO in BuOH, while no changes associated with the deintercalation of DABCO were observed in HDI. Butanol was found to be important for the deintercalation of DABCO. To examine the reactivity of bifunctional monomers, the reaction of 1,4-butanediol (1,4-BDO) and HDI with α-ZrP·DABCO were investigated to show good reactivity at 80 °C and stability at 40 °C.

Band structure database of layered intercalation compounds with various intercalant atoms and layered hosts

Here we provide a database comprising electronic band structures of 9,004 layered intercalation compounds, where atoms are intercalated into a host layered compound with different intercalant atoms, along with 468 structures related to the layered host compounds. Additionally, we provide properties derived from the electronic states such as band gap as well as stability-related properties like formation energies. Direct comparison of the band structures before and after intercalation is generally challenging due to changes in their space group and k-path. However, in this study, we developed new k-paths consistent with the host materials, allowing for the direct comparison of band structures before and after intercalation. This enables direct and quantitative discussion of the band structure changes induced by the intercalations and provides a valuable database for intercalant-driven band engineering. Layered intercalation compounds are widely used in many fields, including superconductivity and energy applications, and understanding of electronic structures is necessary. The feature of our database holds promises for the development of layered compounds with enhanced functionalities through database utilization.

Hierarchical Intercalation of Solvated Tetrafluoroborate Anions into Graphite Electrodes: The Case Studies of Methyl Acetate and γ-Butyrolactone Solutions.

Intercalation of anions unlocks graphite as a positive material in energy storage devices, and the performance could be affected by solvents in solutions. In this context, it is vital to investigate the role of solvents in anion intercalation. Herein, a hierarchical intercalation phenomenon, in which different graphite intercalation compounds are generated in the same solution, is studied in lithium tetrafluoroborate (LiBF4) solutions of carboxylate ester solvents γ-butyrolactone (GBL) and methyl acetate (MA). The evolution modes of the graphite cathode structure during electrochemical intercalation and deintercalation are discussed via in situ X-ray diffraction (XRD) measurements. Based on this, the relationship between GICs and potentials, together with concentrations, is compared in detail. Furthermore, various graphite materials with different surface properties are applied to adjust the anions' solvation status inside graphite sheets.

Intercalation Behavior of a Spiro-bipyrrolidinium Cation into a Graphite Electrode from Dimethyl/Propylene Carbonates.

Quaternary ammonium-graphite intercalation compounds (QA+-GICs) are promising negative electrode materials in dual-carbon batteries by virtue of safety, low cost, and environmental friendliness. However, the intercalation behavior of QA+ into graphite electrodes in mixed solvents has never been reported. Herein, spiro-(1,1')-bipyrrolidinium tetrafluoroborate dissolved in a dimethyl/propylene carbonate (DMC/PC) binary solvent system was employed in graphite/activated carbon (AC) capacitors. The storage behavior of the spiro-(1,1')-bipyrrolidinium cation into graphite is very related to the solvent composition of the electrolyte solutions. In situ X-ray diffraction tests revealed that the graphite electrodes can form different QA+-GICs during cycling, which is a key factor influencing the electrochemical performance of graphite/AC capacitors. Besides, the reversible thickness change of graphite in graphite/AC capacitors with different electrolytes during the charge-discharge process was also addressed. These findings provide sound evidence for the co-intercalation of the solvent with the cation.

In situ X-ray diffraction studies on nominal composition of C2Li under high pressure and temperature

Superdense phase between graphite and Li metal, C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li, has been significant in the research on both lithium-ion batteries (LIBs) and graphite intercalated compounds (GICs). However, a detailed method for synthesizing C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li remains unknown owing to the limited information regarding C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li and difficulties in distinguishing C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li from C6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{6}$$\\end{document}Li. Thus, we performed in situ X-ray diffraction measurements on samples with the nominal composition of C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li under high pressures and temperatures of up to 10 GPa and 400 ∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }\\hbox {C}$$\\end{document}, respectively. We employed two types of C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li samples; one was a mixture of C6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{6}$$\\end{document} graphite powder and Li metal (C6+3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{6}+3$$\\end{document}Li), and the other was a mixture of C6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{6}$$\\end{document}Li and Li metal in which the C6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{6}$$\\end{document}Li was prepared by the electrochemical discharge (reduction) reaction that occurs in LIBs. Considering changes in the d-value based on the 001 diffraction peak from C6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{6}$$\\end{document}Li or C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li, C6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{6}$$\\end{document}Li + 2Li is suitable for synthesizing C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{2}$$\\end{document}Li, although the nonaqueous electrolyte used for the electrochemical reaction should be removed to avoid structural transformations to lower-stage compounds such as C12\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{12}$$\\end{document}Li and C18\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_{18}$$\\end{document}Li during the heating. These findings pave the way toward a method for synthesizing C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document}Li, which could increase the energy density of LIBs and establish GICs with novel physical and electronic properties.

Self-Standing vanadium oxide pillared carbon microfiber film as an excellent anode for lithium & sodium ion batteries

Insertion of substances (such as atoms/molecules/ions) into the interlayer spaces of graphite to increase its layer separation is found to be extremely useful for sodium-ion batteries (SIBs). Therefore, expanded graphitic systems are the obvious choice as anode material for both lithium/sodium-ion batteries (LIBs/SIBs). Hard carbon-based materials altogether give a decent electrochemical performance, as well as allow structural integrity for long-term use. Herein, we report a facile route to prepare free-standing vanadium oxide doped carbon microfibers (V@CMFs) films. The V@CMFs show ∼ 200 % expansion in the graphitic interlayer distances while accommodating minute deformations in the final compound which is further theoretically verified as the stage-1 type dilute graphite intercalation compound (GICs) with pillar-like structures. Best battery performance was obtained for the 1 % doped (V1@CMFs) sample, with an initial discharge capacity of 1501.8 and 703.4 mAhg−1, reversible capacities of 1253.8 and 288.7 mAhg−1 at 20 mAg−1, and rate capabilities i.e., 362.4 and 108.1 mAhg−1 at 1600 mAg−1, for LIBs and SIBs, respectively. The results revealed that the rate capability and the reversible specific capacity of the 1 % vanadium oxide doped carbon microfibers (V1@CMFs) are significantly superior compared to the pristine and previous reports. Here, the incorporation of just 1 % vanadium oxide acts as a pillar, enhancing the stability and conductivity of the carbon. Thus, the present work highlights the utility of molecularly doped GICs as potential anode materials for LIBs/SIBs.

High-Energy Sodium Ion Batteries Enabled by Switching Sodiophobic Graphite into Sodiophilic and High-Capacity Anodes.

Owing to the crustal abundance of sodium element, sodium ion batteries (SIBs) are considered a promising complementary to lithium-ion battery for stationary energy storage applications. The cointercalation chemistry enables the use of cost-effective graphite as anodes, whereas the low capacity (<130 mAh g-1) and high redox potential (>0.6 V vs. Na/Na+) of graphite significantly limit the energy density of SIBs. Herein, we induce the high-capacity Na metal into sodiophilic ternary graphite intercalation compounds (t-GICs) via co-intercalation and deposition reactions, thereby achieving Na/t-GIC anodes with high capacities and low working voltage (0.18 V). The new anodes exhibit high coulombic efficiencies of above 99.7 % over 550 cycles and a high-rate capacity of 588.4 mAh g-1 at 6 C (10 min per charge). When it is paired with Na3V2(PO4)2F3 (NVPF) cathodes, the SIBs demonstrate a high energy density of 259 Wh kg-1 both electrodes surpassing that of commercial LiFePO4//graphite batteries. The outstanding anode performance is attributed to the tailored sodiophilicity of graphite through manipulating the ether solvents and the in situ generated space among t-GIC flakes to stably accommodate Na metal. Our findings for stable Na plating/striping on sodiophilic graphite materials provide an effective approach for developing advanced SIBs.

High‐Energy Sodium Ion Batteries Enabled by Switching Sodiophobic Graphite into Sodiophilic and High‐Capacity Anodes

AbstractOwing to the crustal abundance of sodium element, sodium ion batteries (SIBs) are considered a promising complementary to lithium‐ion battery for stationary energy storage applications. The cointercalation chemistry enables the use of cost‐effective graphite as anodes, whereas the low capacity (&lt;130 mAh g−1) and high redox potential (&gt;0.6 V vs. Na/Na+) of graphite significantly limit the energy density of SIBs. Herein, we induce the high‐capacity Na metal into sodiophilic ternary graphite intercalation compounds (t‐GICs) via co‐intercalation and deposition reactions, thereby achieving Na/t‐GIC anodes with high capacities and low working voltage (0.18 V). The new anodes exhibit high coulombic efficiencies of above 99.7 % over 550 cycles and a high‐rate capacity of 588.4 mAh g−1 at 6 C (10 min per charge). When it is paired with Na3V2(PO4)2F3 (NVPF) cathodes, the SIBs demonstrate a high energy density of 259 Wh kg−1both electrodes surpassing that of commercial LiFePO4//graphite batteries. The outstanding anode performance is attributed to the tailored sodiophilicity of graphite through manipulating the ether solvents and the in situ generated space among t‐GIC flakes to stably accommodate Na metal. Our findings for stable Na plating/striping on sodiophilic graphite materials provide an effective approach for developing advanced SIBs.

Strategic approaches to observing 39K NMR signals from potassium–graphite intercalation compounds

Abstract Solid-state nuclear magnetic resonance is an invaluable tool for potassium–graphite intercalation compounds, promising anode materials of K-ion batteries, but it has not yet been applied because of several issues. We attempted 39K NMR measurements of potassium–graphite intercalation compounds sealed in glass using an 18.8 T NMR spectrometer with a nuclear magnetic resonance probe adjusted to the samples. The first observed 39K NMR signal of potassium–graphite intercalation compounds showed the possibility of evaluating intralayer density, which cannot be ascertained from Raman measurements.

Quantification of solvent-mediated host-ion interaction in graphite intercalation compounds for extreme-condition Li-ion batteries

Achieving simultaneous fast-charging capabilities and low-temperature adaptability in graphite-based lithium-ion batteries (LIBs) with an acceptable cycle life remains challenging. Herein, an ether-based electrolyte with temperature-adaptive Li+ solvation structure is designed for graphite, and stable Li+/solvent co-intercalation has been achieved at subzero. As revealed by in-situ variable temperature (−20 °C) X-ray diffraction (XRD), the poor compatibility of graphite in ether-based electrolyte at 25 °C is mainly due to the continuous electrolyte decomposition and the in-plane rearrangement below 0.5 V. Former results in a significant irreversible capacity, while latter maintains graphite in a prolonged state of extreme expansion, ultimately leading to its exfoliation and failure. In contrast, low temperature triggers the rearrangement of Li+ solvation structure with stronger Li+/solvent binding energy and shorter Li+–O bond length, which is conducive for reversible Li+/solvent co-intercalation and reducing the time of graphite in an extreme expansion state. In addition, the co-intercalation of solvents minimizes the interaction between Li-ions and host graphite, endowing graphite with fast diffusion kinetics. As expected, the graphite anode delivers about 84% of the capacity at room temperature at −20 °C. Moreover, within 6 min, about 83%, 73%, and 43% of the capacity could be charged at 25, −20, and −40 °C, respectively.

Oscillating Structural Transformations in the Electrochemical Synthesis of Graphene Oxide from Graphite.

Electrochemical synthesis of graphene oxide (GO) is known to occur with potential oscillations, but the structural changes underlying these oscillations have remained unclear. In situ time-resolved synchrotron radiation X-ray diffraction demonstrates that the electrochemical synthesis of GO in aqueous H2SO4 can be described as an oscillating reaction. The transformation from graphite to GO proceeds through periodic structural oscillations that correlate with potential cycles. Stage-1 graphite intercalation compound (GIC) is found only at the peak of the potential cycle, but not at the bottom of the cycle. Stage-1 GIC is formed in the first half-cycle from stage-2 GIC and then transforms into "pristine graphite oxide" (PGO) on the lower side of the potential cycle, after which the cycle restarts with the formation of a new portion of stage-1 GIC. Water-washing results in the transformation of PGO into water-swollen GO with d(001) ~11 Å. These periodic structural changes can be considered a new type of oscillating reaction. The presented results provide broad insights into the oscillating structural changes occurring during the anodic graphite oxidation in aqueous H2SO4 and allow to update of the mechanism of GO electrochemical formation.

Oscillating Structural Transformations in the Electrochemical Synthesis of Graphene Oxide from Graphite

AbstractElectrochemical synthesis of graphene oxide (GO) is known to occur with potential oscillations, but the structural changes underlying these oscillations have remained unclear. In situ time‐resolved synchrotron radiation X‐ray diffraction demonstrates that the electrochemical synthesis of GO in aqueous H2SO4 can be described as an oscillating reaction. The transformation from graphite to GO proceeds through periodic structural oscillations that correlate with potential cycles. Stage‐1 graphite intercalation compound (GIC) is found only at the peak of the potential cycle, but not at the bottom of the cycle. Stage‐1 GIC is formed in the first half‐cycle from stage‐2 GIC and then transforms into “pristine graphite oxide” (PGO) on the lower side of the potential cycle, after which the cycle restarts with the formation of a new portion of stage‐1 GIC. Water‐washing results in the transformation of PGO into water‐swollen GO with d(001) ~11 Å. These periodic structural changes can be considered a new type of oscillating reaction. The presented results provide broad insights into the oscillating structural changes occurring during the anodic graphite oxidation in aqueous H2SO4 and allow to update of the mechanism of GO electrochemical formation.

Synthesis, Structure, and Electrochemistry of Crystallized Layered Chlorides, LiMCl6 (M = Ta/Nb)

AbstractA suitable solid electrolyte can turn the long‐standing dream of a safe commercial all‐solid‐statebattery into reality in the same way as appropriate liquid electrolytes kickstarted the first commercial lithium‐ion battery. Presently, halide‐based electrolytes despite their reactivity with lithium metal are extensively studied as they offer better processability, malleability, oxidative stability, and safety over sulfide‐based electrolytes. Particularly, LiMCl6 (M = Ta/Nb) chloride‐based amorphous electrolytes are generating widespread interest with their high conductivities, comparable to liquid electrolytes. In this context, with synchrotron X‐ray and neutron powder diffraction techniques, well‐crystallized triclinic layered LiMCl6 (M = Ta/Nb) chlorides with an hcp AB‐type stacking of chloride ions is reported. The hexagonally ordered NbCl6 octahedra share edges with LiCl6 octahedra forming a honeycomb pattern, whereas Li+ is intermixed with M5+ for M = Ta. Furthermore, it is found that crystalline LiTaCl6 has an ionic conductivity of ≈10−5 mS cm−1, six orders of magnitude lower than that reported for superionic amorphous LiTaCl6. Nevertheless, crystalline LiTaCl6 is utilized as an intercalation compound in an all‐solid‐state‐battery, uncovering a solid‐solution/two‐phase/conversion pathway for lithium‐insertion during the three distinct redox plateaus below 3 V versus Li+/Li°. Broadly, the findings give insights into the structure, ionic conduction, and intercalation in a new family of layered halides.

Unraveling the contribution of nucleation to the intercalation energy barrier for phase-transforming Li-ion battery materials

Phase-transforming intercalation compounds, such as LiFePO4 (LFP) and Li4Ti5O12 (LTO), are widely utilized in Li-ion batteries, particularly for applications requiring high power and operation at low temperatures. However, the impact of phase transformation kinetics on energy density losses under extreme conditions has been largely unexplored. Specifically, the role of nucleation, the initial stage of phase transformation, in contributing to battery performance losses has not been previously investigated. In this study, we not only quantified the significance of material-level factors, such as interfacial charge transfer, in the low-temperature and high-rate performance of LFP and LTO materials, but also provided the first estimates of the apparent activation energies of nucleation. Our findings revealed that nucleation, particularly in the case of LFP, contributes significantly to overpotential, highlighting its pivotal role among material-level factors. Furthermore, our analysis allowed us to differentiate between material-level and particle-level limitations for the LTO/LFP cell, emphasizing the paramount importance of controlling the porosity of secondary particles to ensure high tolerance towards high-rate/low-temperature discharge.

An eco-friendly approach for graphene nanoplatelets by innovative wet thermal expansion and liquid-phase exfoliation

Cost-effective synthesis of high-structural integrity graphene nanoplatelets (GNPs) remains a grand challenge. This study presents an innovative, environmentally friendly and efficient method for synthesizing high-quality GNPs by integrating wet thermal expansion with liquid-phase exfoliation. The thermal expansion of a wet graphite intercalation compound (GIC) in a semi-closed system improves the expansion effectiveness, minimizes the release of fine dust and improves the hydrophilicity of the resulting product. These improvements significantly enhance the effectiveness and efficiency of the subsequent liquid-phase exfoliation by shearing, which produces GNPs in pure water within 30 min with an overall productivity of 38.24 %. GNPs exhibit desirable properties, e.g. few layers (1–2 nm thick), large lateral dimension (a few microns), high sp2 hybridized carbon content (86 %), rich surface functional groups yet a low oxidation level (C/O ratio = 21.7 and electrical conductivity of ∼ 2055 S cm−1). The simplicity, adjustability and scalability of this method, combined with environmental friendliness, make it suitable for various applications and pave the way for further advancements in sustainable nanotechnology practices.

Deciphering the Impact of Current, Composition, and Potential on the Lithiation Behavior of Si-Rich Silicon-Graphite Anodes.

Adding silicon (Si) to graphite (Gr) anodes is an effective approach for boosting the energy density of lithium-ion batteries, but it also triggers mechanical instability due to Si volume changes upon (de)lithiation reactions. In this work, component-specific (de)lithiation dynamics on Si-rich (30 and 70wt.% Si) SiGr anodes at various charge/discharge C-rates are unveiled and compared to a graphite-only electrode (100Gr) via operando synchrotron X-ray diffraction coupled with differential capacity plots analysis. Results show preferential lithiation of amorphous Si above ≈200mV and competing lithiation of Gr, amorphous Si, and crystalline Si below ≈200mV. Discharge proceeds via sequential delithiation of Gr and amorphous lithium silicide. Si shifts the interconversion potentials of graphite intercalation compounds, lowering the Gr state of charge compared to 100Gr. In the 30%Si electrode, crystalline Si amorphization at potentials <110mV is found to be kinetically hindered at C-rates higher than C/5, which can be key for enhancing the cycling stability of SiGr anodes. The 70%Si electrode exhibits restricted lithium diffusion in Gr, full Si amorphization, and Li15Si4 formation. These findings related to the potential- and current-dependent dynamic changes on SiGr blends are crucial for designing stable high energy density SiGr anodes.

Charge transfer in alkaline-earth metal graphite intercalation compounds

The charge transfer from a metal atom towards the carbon layers in first stage graphite intercalation compounds (GIC) is a fundamental issue to explain under which conditions superconductivity sets in and the electronic properties of such ground state. To study in detail the transfer process and its evolution as a function of the nature of the intercalated metal, and especially taking in consideration the interlayer distance, we performed detailed X-Ray Diffraction and Raman scattering measurements on very high-quality bulk intercalated CaC6, SrC6 and BaC6 samples. We combined both the experimental results with detailed density functional theory calculations to give a coherent picture in which it is possible to follow the evolution of the charge transfer to the carbon layer in full agreement with the experimental data. The full comprehension of such mechanism remains a fundamental issue to explain the variation of the superconducting ground state in first stage GIC.

Cluster intercalation of aluminum tetrachloride in AlN cathode: Exploration and analysis of aluminum ion batteries.

When chloroaluminate (AlCl4-) serves as the electrolyte, aluminum nitride (AlN) has shown promise as a cathode material in aluminum ion batteries. However, there is currently a lack of research on the mechanisms of charge transfer and cluster intercalation between AlCl4 and AlN cathode materials. Herein, first-principles calculations are employed to investigate the intercalation mechanism of AlCl4 within the AlN cathode. By calculating the formation energies of stage-1-5 AlN-AlCl4 intercalation compounds with the insertion of individual AlCl4 cluster, we found that the structure of the stage-4 intercalation compounds exhibits the highest stability, suggesting that when the clusters begin to intercalate, it is important to start with the formation of the stage-4 intercalation compounds. In the subsequent phases of the charging process (stages 1 and 2), the stabilized structure with four inserted clusters demonstrates two characteristics: the coexistence of standing and lying clusters and the insertion of two standing clusters in an upside-down doubly stacked configuration, which further improve the spatial utilization while maintaining the structural stability. In addition, we infer that a phenomenon of coexisting intercalation compounds with mixed stages will occur in the course of the charging and discharging processes. More importantly, the diffusion barrier of AlCl4 in AlN-AlCl4 intercalation compounds decreases with the reduction of stage number, ensuring the rate performance of batteries. Therefore, we expect that our work will contribute to comprehend the intercalation mechanism of AlCl4 into the AlN cathode materials of aluminum ion batteries, providing guidance for related experimental work.

Sodium into γ-Graphyne Multilayers: An Intercalation Compound for Anodes in Metal-Ion Batteries.

The bulk synthesis of γ-graphyne has been recently achieved and evidenced a multilayered structure, which suggests its potential exploitation as a substitute of graphite-based anode materials for metals heavier than lithium (Li). In fact, each of its regular pores of sub-nanometric size features an optimal environment for hosting a single sodium (Na) ion, as reported here by means of accurate electronic structure calculations. We show that the graphyne/Na ion coupling mimics that found on the graphene/Li ion in terms of metal-single layer interaction and equilibrium distance. More importantly, in contrast to what is found for graphite, we demonstrate that graphyne intercalation compounds with Na are thermodynamically stable and feature an optimal storage capacity of 372 mAh·g-1. These findings, together with a limited crystal structure expansion upon Na intercalation, a low metal diffusion barrier as well as high electrical conductivity, pave the way to the development of novel graphyne-based anodes for efficient Na-ion batteries.